


Lesson One

by PineByPine (Tyrannosaurus_Sex)



Category: Gravity Falls
Genre: Aged-Up Character(s), F/F, fem!Dipper
Language: English
Status: Completed
Published: 2019-07-05
Updated: 2019-07-05
Packaged: 2020-06-09 17:47:07
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,365
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19480909
Author URL: https://archiveofourown.org/users/Tyrannosaurus_Sex/pseuds/PineByPine
Summary: An Identical Twins AU flick. Dipper teaches Mabel the finer points off... some dirty stuff.





	Lesson One

**Author's Note:**

> This was the explicit companion to a much larger fic set in the same Identical Twin AU. In hindsight, I'm uncomfortable with that fic as a whole, but if you excise this bit, it's still pretty good.

“Look, it’s fine. You don’t have to if you don’t want to.”

“It’s not that I don’t want to, Dippinstuff. It’s the freakin’ performance pressure”

“What pressure? It’s just a vagina; it’s not a studio audience.”

Mabel flopped dramatically against the pillow. “Blargh!”

“Sorry I brought it up, Mabes. I didn’t mean to touch a sore spot.”

“It’s not a sore spot, you dork. It’s just…” She growled in frustration. “How do I put this? You’ve done for that for me already and it was great.”

Dipper smiled, “I’m glad you liked it.”

Mabel rolled, threw a leg over her sister’s lap, and grabbed her face in both hands; smooshing Dipper’s cheeks together. “You don’t understand. It was fantastic. It was amazing. You are the absolute best. I literally didn’t think anything could be that good ever and now you’ve proven you can do it over and over again. I am in big O paradise over here.”

The smooshed cheeks under Mabel’s palms started to turn a light pink color and Dipper looked a little nervous. 

“What I am saying is: how the heck am I supposed to follow that?” A look of confusing flashed across Dipper’s face. Mabel released her grip, rolled off of her, and buried her face in the pillow. “You set the bar so high! I’m never going to clear it.”

Dipper gave her a sweet little smile. “Well you don’t exactly get good at something by never trying.”

“Say that when you’re looking a hoo-hah in the face and trying to figure out what to do with it.”

“It’s not like you’re unfamiliar with the lay of the land down there. Just, you know, dive in. I’ll let you know what works and what doesn’t.”

Mabel made another frustrated noise, muffled by the pillow. Dipper leaned over, brushed some hair away from her sister’s shoulder, and kissed the smooth skin there a few times. “Look at it this way: if I’m so good, don’t you think I could be a good teacher?”

The older girl rose on her elbows and gave her a sharp look. “You’ll reveal your secrets?”

“It’s in my best interest to tell you everything I know.” She drew in and kissed Mabel’s lips, lingering there. She put a hand to the back of her sister’s head and lay back against the bed, pulling her along for the ride. Dipper’s bare legs wrapped around Mabel’s body and instinctively Mabel arched her back against her.

Mabel broke the kiss and planted another on the line of Dipper’s jaw, then on her neck, throat, collarbone all the way down until she put her lips on a nipple, standing brazenly on the small mound of Dipper’s breast. She flicked her tongue over it, then drew it into her mouth and was pleased by the small moan that escaped her sister’s lips. She slid a hand down along Dipper’s ribs and stomach, past her hip to run fingertips over the creamy skin of her thigh.

“Yep,” Dipper said breathlessly, “that’s right on the money.”

Mabel continued her trajectory down, leaving a trail of kisses across Dipper’s stomach. With a gentle hand, she kept her sister’s legs apart, took a steadying breath, and looked over her foe. As an owner of one of these, she was in theory pretty familiar with the anatomy, but it wasn’t like she’d seen one from this direction very often. Dipper was a long time waxer, so the image presented to Mabel was not unlike the diagrams in her old health textbooks.

“Um, Mabel. Is everything ok? You’ve been staring for a little while.”

Mabel shook her head and realized that she had frozen up for an indeterminate period of time. She blushed, embarrassed. “Yea, sorry. Just not sure where to start.”

“You don’t have to go right in; you can sneak up on it.”

She leaned down and put her lips to the inside of Dipper’s thigh, then kissed that transitional area between stomach and thigh. She worked her way around the area, kissing, nibbling, growing closer slowly until her lips were grazing against the exposed lips of her sister’s vulva. She heard a sharp intake of breath from above and looked up to see Dipper holding her hand over her own mouth, eyes shut tightly.

“That’s good. Slow, light at first.” She said through the fingers of her hand.

Mabel placed her open mouth against the sweet skin of Dipper’s nethers. She went slow; her touch was light.

“You can vary it up and escalate, but if you find something I really like hold that tempo and what you’re doing. It’ll be tempting to ramp it up but just hold steady.”

The older twin pulled back a little to speak. “And just how am I supposed to know when to do that?”

“I’ll…” Dipper’s squirmed at the break in contact. “It’s on me to let you know, but I hope it’ll be obvious.  _ You’re _ pretty obvious.”

Mabel smiled and went back to the task at hand. She moved focus from her lips to her tongue and increased the pressure a little. The response from her sister grew in intensity to match. She made a series of little moans and actually bucked her hips a little against Mabel’s mouth.

“You can…” Dipper spoke between noises of pleasure. “You can use your fingers too. I’ve got some lube somewhere if you need it.” She didn’t need it; Dipper was so wet that Mabel’s finger slipped in easily. She felt the softness around her finger and found she still hand enough room to put her lips and tongue back to work. “If you kind-” heavy breath “-kind of curve your finger toward you-” a sort of convulsive moan, “-you should feel a sort of spongy spot.”

Mabel followed her sister’s guidance and felt the spot in question. She felt a shiver run through Dipper’s body and saw her take in a fist full of bedsheets in between clenched fingers. “Yes, just like that. God damn you’re sexy, Mabes.”

She did her best to keep her ministrations steady as Dipper’s expressions of bliss rose in a steady climb. She wriggled a little and managed to snake her free hand beneath her own body and down the front of her panties. Mouth, tongue and both hands thus engaged was a bit like trying to rub her stomach and pat her head at the same time, but the noises Dipper was making and the uncontrolled, writhing way she was moving was just more than Mabel could stand.

“Oh my god, fuck fuck fuck…” Dipper’s words became an unintelligible mumble. Mabel felt a hand on the back of her head, fingers digging through her thick hair and fingernails lightly scratching her scalp. Her sister made an animalistic scream and every muscle in her body went stiff, actually pushing her pelvis up off the bed. Mabel stuck with her and had to abandon her own pleasure to use that hand to steady herself. Overcome with excitement, she sped up and pressed a little harder, turning everything she was doing up by just a little. Dipper’s climax lasted for a long time before she collapses, panting and sweating, back to the surface of the bed.

Mabel slunk back up and curled around her sister’s suddenly limp form. Her wet lips brushed over Dipper’s ear. “Ok, so I guess you’re not a half bad teacher for a nerd.”

Dipper let out a huge sigh. “Mabel, you’re a natural; that was the best.”

Mabel pumped her fist in the air. “Woot woot! I am the Queen of Sex!”

The younger twin rolled over to lie face to face and kissed her. “What does that make me? You had some very flattering things to say earlier.”

Mabel considered it. “Well, that was before you’d unleashed my full potential on the world.” She crept her hands down to cup Dipper’s cute little butt. “Tell you what, I’m ready for my turn; do good job and I’ll name you the Duchess of Orgasms.”

Dipper rolled on top of her sister and pinned her to the bed, smiling wickedly. “Oh no, that’s won’t do; I’m coming for your crown, missy.”


End file.
